Figure 1. Astrocyte syncytial isopotentiality.

(A) In a single freshly disassociated astrocyte, K⁺-free/Na⁺ pipette solution [Na⁺]_P progressively substituted the endogenous K⁺ content in whole-cell recording, leading to a V_M depolarization towards 0 mV as predicted by Nernstian equation. (B) The V_M recorded from an astrocyte in situ with [Na⁺]_P disobeys the Nernstian prediction. Instead, the V_M maintains at a quasi-physiological level. (B2) In [Na⁺]_P recording, the initial V_M (V_M,_I), and the quasi-physiological V_M at the steady-state (V_M,_SS). Input resistance (R_In) was periodically monitored during recording. (C) V_M,_SS was significantly more depolarized than V_M,_I (p < 0.001, pairwise t-test). (D) V_M,_I and V_M,_SS was measured in whole-cell recording using 140 mM KCl recording pipette ([K⁺]_P). (E) V_M,_I in [K⁺]_P and [Na⁺]_P recordings was not significantly different (p > 0.05, unpaired t-test). (F) The relationship between V_M,SS and coupling strength (S) predicted by computational modeling. The V_M,SS from hippocampal CA1 syncytium, −73 mV, is used as the baseline in the model to predict the relative difference in coupling strength (S%) between CA1 syncytium and a syncytium of another brain region.